Olivine‐Type MgMn_0.5Zn_0.5SiO₄ Cathode for Mg‐Batteries: Experimental Studies and First Principles Calculations

Abstract

model to unveil enhanced reactions in lithium and magnesium battery fields. [2,3] One of the main limitations of the LFP is the limited capacity for one electron reaction and thus its energy density cannot get over to that of layered oxides. Therefore, alternative silicates with Li 2 MSiO 4 (M = Mn, Fe, Co, Ni) stoichiometry are currently studied due to the high theoretical capacity of 333 mA h g −1 . [4,5] Additionally, the redox potential should be successfully monitored by the redox (≈manganese) active species. Importantly, the main instabilities caused in the original Mn-tetrahedral environments, structural amorphization during alkali metal extraction and structural distortions should be abated. [5] This study compares different manganese silicates with Mn in octahedral environment to avoid the instabilities of Mn in tetrahedral sites. Specifically, MgMnSiO 4 is used as a model which has an olivine-type structure (similar to LFP) where Mg atoms occupy the so-called M1 site (as Li in LFP) while Mn atoms occupy the M2 site (Fe in LFP) (Scheme 1). The chemical formulation is thus (Mg) M1 (Mn) M2 SiO 4 . [6,7] Additionally, the comprehensive exchange of Mg and Mn in their respective sites gives the following cation distribution: (Mg 1-y Mn y ) M1 (Mg y Mn 1-y ) M2 SiO 4 , being the degree of exchange dependent on the sample thermal history. [8,9] This work aims to determine the structure and Mg extraction/insertion properties from/into (Mg) M1 (Mn 0.5 Zn 0.5 ) M2 SiO 4 . The replacement of half amount of Mn atoms in the octahedral sites by other divalent elements such as Zn 2+ could have an impact on the voltage and the energy density as foreseen by DFT calculations. The calculated voltage during Mg reaction for MgMnSiO 4 is ≈2.9 V, while the higher voltage of ≈3.2 V is obtained in the case of (Mg) M1 (Mn 0.5 M 0.5 ) M2 SiO 4 (M = Ca and Ni). However, the higher atomic weight of Ni penalizes its energy density, as compared with lighter elements such as M = Ca or Mg. The (Mg) M1 (Mn 0.5 Zn 0.5 ) M2 SiO 4 cathode achieves experimentally 120 mA h g −1 with an average voltage of ≈2 V. Results and Discussion Structure and Mg Extraction: Case of MgMnSiO 4The calculated unit cell parameters (a = 10.460( 5) Å, b = 6.134(3) Å, c = 4.817(2) Å, and V = 309.0(2) Å 3 ) from the refined X-ray diffraction (XRD) pattern are in good agreement with previous Magnesium driven reaction in olivine-type MgMn 0.5 Zn 0.5 SiO 4 structure is subject of study by experimental tests and density functional theory (DFT) calculations. The partial replacement of Mn in Oh sites by other divalent metal such as Zn to get MgMn 0.5 Zn 0.5 SiO 4 cathode is successfully developed by a simple sol-gel method. Its comparison with the well-known MgMnSiO 4 olivine-type structure with (Mg) M1 (Mn) M2 SiO 4 cations distribution serves as the basis of this study to understand the structure, and the magnesium extraction/insertion properties of novel olivine-type (Mg) M1 (Mn 0.5 Zn 0.5 ) M2 SiO 4 composition. This work foresees to extend the study to others dival...

The Magnesium Insertion Effects into P2‐Type Na2/3Ni1/3Mn2/3O2

“…As a complementary to the rechargeable lithium and sodium ion batteries, the magnesium batteries have attracted enormous DOI: 10.1002/smll.202305690 attention due to their cost-effective and environmentally friendly features. [1] Indeed, the dendrite-free properties of metallic magnesium employed in the anode side are opening new opportunities to develop safe and high volumetric capacity meal batteries. [2][3][4][5] Regardless of the progress found during the past few years, development of a practical Mg reversible battery remains a big challenge mainly due to the limited compatibility of Mg-intercalation cathodes with the anode and electrolytes.…”

Rational Design of Ni-Doped V2O5@3D Ni Core/Shell Composites for High-Voltage and High-Rate Aqueous Zinc-Ion Batteries

“…Generally, the narrow interlayer spacing and poor electronic conductivity of vanadium-based materials can lead to slow reaction kinetics and unstable structures during the Zn 2+ (de)incorporation process, limiting their applications in ZIBs [ 32 ]. For this issue, the incorporation of metal ions, such as Na + , Li + , Mg 2+ , Mn 2+ , and Cu 2+ [ 33 , 34 , 35 , 36 , 37 ], has been classified as one of the most effective strategies to enlarge interlayer spacing. In addition, metallic element incorporation adjusts the composition of V-based materials while changing their structures and thus improves electronic conductivity [ 38 ].…”